Iodination iodide

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Jod-. iodine, iodide of, iodo-, iodated, -alkyl, n. alkyl iodide, -allyl, n. allyl iodide, -ammon,... 

The normal reduction potential of the iodine-iodide system is independent of the pH of the solution so long as the latter is less than about 8 at higher values iodine reacts with hydroxide ions to form iodide and the extremely unstable hypoiodite, the latter being transformed rapidly into iodate and iodide by self-oxidation and reduction ... 

Discussion. Iodine (or tri-iodide ion Ij" = I2 +1-) is readily generated with 100 per cent efficiency by the oxidation of iodide ion at a platinum anode, and can be used for the coulometric titration of antimony (III). The optimum pH is between 7.5 and 8.5, and a complexing agent (e.g. tartrate ion) must be present to prevent hydrolysis and precipitation of the antimony. In solutions more alkaline than pH of about 8.5, disproportionation of iodine to iodide and iodate(I) (hypoiodite) occurs. The reversible character of the iodine-iodide complex renders equivalence point detection easy by both potentiometric and amperometric techniques for macro titrations, the usual visual detection of the end point with starch is possible. 

Measure the transmittance of the solution at 840 nm or with a red filter with maximum transmission above 700 nm. Charge the reference cell with a solution obtained by taking the iodine-iodide-hydrogencarbonate mixture and treating it with molybdate-hydrazinium sulphate-disulphite as in the actual procedure. 

Construct the calibration curve by taking, say, 0, 2.5, 5.0, 7.5, and 10.0 ftg As (for a final volume of 10 mL), mixing with iodine-iodide-hydrogencarbonate solution, adding molybdate-hydrazinium sulphate-disulphite, and heating to 95-100°C. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

The reaction between starch and iodine (or iodine-iodide mixtures) to form an inclusion compound was first reported in 1814 by Colin and de Claubry 131) and has since become familiar to all chemists through its applications in analytical chemistry. Its deep blue colour (kmax 620 nm) has been known for years to result from a linear arrangement of polyiodide within a canal formed by a helical coil of amylose. The helical amylose structure will trap other molecules 132,1331 and other hosts will stabilise polyatomic iodide guests134> 135). 

This helical arrangement of amylose, known as the V-form, may be precipitated from certain solutions (e.g. in butanol or DMSO) of amylose. Either hydrated (Vh-) or anhydrous (Va-) amylose absorbs I2 vapour to produce the blue compound with the necessary I" being produced in situ. Alternatively the compound may be formed from iodine-iodide mixtures in solution which allows the V-form to be produced and stabilised as the polyiodide compound 141 The compound was reported 142) to have the orthorhombic space group 7>212121. 

The E°i(ads) values obtained here indicate that, upon surface coordination, the redox potential of the iodine/iodide couple is shifted in the negative direction by about 0.90 V on Au, 0.76 V on Pt, and 0.72 V on Ir. These chemisorption-induced redox potential shifts can be employed to estimate the ratio of the formation constants for surface coordination of iodine and iodide ... 

One way to determine the vitamin C content of a sample is to titrate it with an iodine/iodide solution. The diagram below shows the reaction involved. 

Baleux B. Colorimetric determination of nonionic, poly(oxyethylene) surface-active agents using an iodine-iodide solution. CR Acad Sci Sci Chim 1972 274 1617. 

The cathode materials employed for the early lithium-based systems were 3.0 V class oxides or sulfides thus, the redox potential for the additive should be located in the neighborhood of 3.2—3.5 V. Accordingly, the first generation redox additive proposed by Abraham et al. was based on the iodine/ iodide couple, which could be oxidatively activated at the cathode surface at 3.20 V and then reduced at the lithium surface. " " " 2° For most of the ether-based solvents such as THF or DME that were used at the time, the oxidation potential of iodide or triiodide occurred below that of their major decompositions, while the high diffusion coefficients of both iodine and iodide in these electrolyte systems ( 3 x 10 cm s ) offered rapid kinetics to shuttle the overcharge current. Similarly, bromides were also proposed.Flowever, this class of halide-based additives were deemed impractical due to the volatility and reactivity of their oxidized forms (halogen). 

Iodine, hydrogen peroxide titration, 627 Iodine-iodide buffer, potentiometry, 699 Iodine number, unsaturated polyolefins, 740 lodobenzene, dioxirane oxidation, 1158 lodohydrins, dioxirane oxidation, 1158 lodometry... 

Potentiometry biosensors, 664 fitness for purpose, 663 hydrogen peroxide determination, 650-1 iodine-iodide buffer, 699 measurement uncertainties, 663 peroxide value, 663-4 transition metal peroxides, 1069 POV see Peroxide value POZ see Primary ozonides Precipitation waters, hydrogen peroxide determination, 637... 

Figure 6.2-12 Cyclic voltammogram of 0.1 - 1 mmol dm Geb on gold in dry [BMIMj PFg , starting at-500 mV towards cathodic (a) and anodic (b) regime. Two quasireversible (E, and E2) and two apparently irreversible (E4 and E5) diffusion-controlled processes are observed. E3 is correlated with the growth of two-dimensional islands on the surface, E4 and E5 with the electrodeposition of germanium, Ej with gold step oxidation, and E, probably with the iodine/iodide couple. Surface area 0.5 cm (picture from [59] - with permission of the Peep owner societes).

Dye sensitization of a nanometer-sized Ti02 powder film soaked in an organic medium containing iodine/iodide redox electrolytes successfully generated open circuit photovoltage (Foe) 0.68 V, Jsc 11.2 mAcm-2, Fill factor (FF) 0.68, and... 

Inspection of Table II shows that a variety of iodine products are formed with the iodine in several oxidation states. Thus fixation materials with iodine as complexed elemental iodine, iodide, and iodate, must be evaluated, and the solid fixation matrix selected must be able to accept a variety of materials. 

The latex was cleaned by ion exchange and serum replacement, which gave the cleaned latex plus six serum fractions. The cleaned latex and the serum samples were analyzed by conductometric titration. Also, the amount of anionic emulsifier in the serum was determined by Fyamine 1622 colorimetric titration and thin-film chromatography, and the amount of nonionic emulsifier by iodine-iodide colorimetric titration and thin-film chromatography. 

The material balance of the strong-acid groups showed a theoretical total of 0.194 meq/gm polymer from the sodium lauryl ether sulfate, potassium persulfate, and sodium hydrosulfite, in comparison with a measured total of 0.205 meq/gm (0.026 on particle surface 0.179 in serum) by serum replacement and a total of 0.215 meq/gm by ion exchange with Dowex 50W(H+). The material balance of the acrylic acid showed that 29.9% was on the particle surface, 28.6% in the aqueous serum, and 41.5% buried inside the particle. The sodium lauryl ether sulfate found in the serum amounted to 78% of that added by Hyamine 1622 titration and 88% by thin-film chromatography. The nonylphenol polyoxyethylene adduct amounted to 113% by iodine-iodide titration and 91% by thin-film chromatography. ... 

Figure 6.13 Schematic of a solar cell based on Ti02 sensitized with an electron donor (D) and the electron relay, iodine/iodide. Reproduced by permission of Wiley-VCH from A. C. Lees, B. Evrard, T. E. Keyes, J. G. Vos, C. J. Kleverlaan, M. Alebbi and C. A. Bignozzi, Eur.. Inorg. Chem., 2309 (1999)...

Figure 6.40 Schematic of a photovoltaic cell based on NiO modified with an electron donor and in the presence of the electron relay iodine/iodide...

The preparation of starch blue in aqueous solution with iodine-iodide mixtures is the most common procedures. According to the method of Pals56 starch (10 mg) of water (5 mL) is boiled for 5 min and blended with 7.6 X 10 5 mol/L (5 mL) of an aqueous solution of iodine and 4.27 x 10 5 mol/L (5 mL) of an aqueous solution of KI. The complex is precipitated by the addition of an aqueous solution of KF (10 mol/L). The precipitate is centrifuged (5000 rpm for 10 min) and washed with aqueous KF (1 mol/L). The Vanino reagent (barium permanganate) also precipitates iodized starch.57 The resulting complex is stable and has a defined stoichiometry. A similar procedure was described by Meyer and Bemfeld.58 Chinoy... 

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